1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, a recording apparatus, and the like, and more specifically relates to a construction for positioning an intermediate transfer belt.
2. Related Background Art
An image forming apparatus for recording an image while conveying a sheet may be so constructed that a part of the apparatus can be swingably opened and closed, for the purpose of removing a jammed sheet or exchanging an internal unit. On this occasion, a part of the apparatus constructing the image forming apparatus, such as a sheet conveying unit, a fixing unit and the like may be disposed on a swing section serving also as an outer package.
For example, the image forming apparatus comprises an intermediate transfer belt as a belt member, a first swing section for supporting a fixing unit, a secondary transfer roller as a sheet conveying unit and the like and forming a part of an output tray, and a second swing section for supporting an intermediate transfer belt, in which the first swing section and the second swing section are so constructed as to swing around different fulcrum shafts, respectively.
In a swing construction shown in Japanese Patent Application Laid-Open No. 2003-156984 (FIG. 6, FIG. 8, and FIG. 10), the intermediate transfer belt is directly fixed to the second swing section. Therefore, the intermediate transfer belt is positioned through at least two parts of a chassis which bears the fulcrum shaft of the second swing section, and the second swing section.
Further, similarly, the secondary transfer roller also is positioned through at least two parts of a chassis which bears the fulcrum shaft of the first swing section for supporting the secondary transfer roller, and the first swing section.
That is, stabilization of the output image requires that the intermediate transfer belt and the secondary transfer roller abut each other with a high accuracy of position. However, according to the above-mentioned construction, the accuracy of position of the secondary transfer roller with respect to the intermediate transfer belt depends on the accuracies of the respective parts and the attaching accuracies of all the chassis (the rotating fulcrum shaft of the second rotating section), the chassis (the rotating fulcrum shaft of the first rotating section), and the first rotating shaft.
On this occasion, a problem has been caused as a result of the accuracy of position of the intermediate transfer belt lowering with respect to an apparatus main body, when the intermediate transfer belt and the secondary transfer roller are abutted to each other.